What Causes Reappearance Of Yellow Pus Spots On Nipples Which Leaves Open Sores?

I'm a breast feeding mom of 36, normal weight, average height, non-drinker, non-smoker, some small allergies including to latex - baby is 8 months old - and yellow puss spots - like hives - keep reappearing on my nipples. They diappear when she feeds, but leave me with cracked nipples like open sores - any ideas? help!